1. Understanding Proportion

2. Ratio A ratio is the comparison of two numbers by division. A classroom has 16 boys and 12 girls. Also written as16 boys, 16:12 or 16 to 12 12 girls Generally, ratios are in lowest terms: 16 = 16/4 = 4 12 12/4 3

3. Ratio, continued Ratios can compare two unlike things: Joe earned $40 in five hours The ratio is 40 dollars or 8 dollars 5 hours 1 hour When the denominator is one, this is called a unit rate.

4. Now, on to proportions! What is a proportion? A proportion is an equation that equates two ratios

5. Properties of a proportion? 2x6=12 3x4 = 12 3x4 = 2x6 Cross Product Property

6. How about an example? Solve for x: 7(6) = 2x 42 = 2x 21 = x Cross Product Property

7. How about another example? Solve for x: 7x = 2(12) 7x = 24 x = Cross Product Property Can you solve it using Reciprocal Property? If yes, would it be easier?

8. Proportion, continued Tires cost two for $75. How much will four tires cost? # of tires 2 = 4 so 2 x 2 = 4 tires cost 75 n 75 x 2 $150 n = 150, so four tires cost $150

9. Proportion, continued Now you try! Three cans of soup costs $5. How much will 12 cans cost? # of cans 3 = 12 3 x 4 = 12 cans cost 5 n 5 x 4 20 dollars n = 20, so 12 cans cost $20